Is there a problem with the On-Rev email server

[Kay C Lan]

Just sent an email to my mum, old address nothing changed, and I
received this Mail Delivery System message:

554 Your access to this mail system from 46.105.105.217 has been
rejected due to the sending MTA's poor reputation.

46.105.105.217 is nowhere near my current IP address.

The SMTP server I'm using is on-rev. A search for the above IP address
indicates it's in France. Is on-rev in France now? I'm on the diesel
server.

The email, which included half a dozen addresses, all went to the
other recipients, only the one was rejected.

Should I be worried about this? Is it likely to be temporary and I
should try again tomorrow. Should I contact on-rev support at:

http://on-rev.com/support/contact-us/

If it isn't on-rev where else should I be looking?

Using Mail 7.3, OS X 10.9.5

Any advice appreciated.